Grzegorz Pieton, 26, had been driving a tractor when its trailer made contact with the 11,000 volt overhead cables at Belmont Nursery, Terrington St Clement.

He had been moving soil at the firm, which produces cut flowers and bulbs for companies that supply supermarket chains.

Mr Pieton, a Polish national who had a wife and young daughter, died on July 15, 2010 in the peony field off Long Road.

A nearby resident had found him after seeing “dark-coloured smoke” over the top of her bungalow.

She called the emergency services and Mr Pieton was taken to the Queen Elizabeth Hospital in King’s Lynn by ambulance and pronounced dead at 11.18am.

It took the jury of seven men and five women five hours and six minutes to find owning company PS and JE Ward, based in King’s Lynn, guilty of failing to ensure the safety of an employee but not guilty of corporate manslaughter.

At Norwich Crown Court this week Judge Stephen Holt adjourned sentencing until June 6 and indicated it would be a financial penalty.

When the Crown Prosecution service announced it would face charges, PD & J Ward said it had worked closely with police, the Health and Safety Executive and other agencies investigating the incident.

“Everyone at Belmont Nursery remains profoundly saddened by the death of Mr Pieton,” it added. “And his family have been, and are constantly, in our thoughts.”

The court had earlier been told that Mr Pieton had not been trained to drive the tractor.

PS and JE Ward mostly employed workers from Poland, Lithuania and Latvia but did not translate most health and safety literature and relied on other workers to act as interpreters, prosecutors told the court.

They also said the company had grown trees around the base of the power line poles, thereby obscuring the warning signs that said ‘danger of death.